The invention relates to an apparatus for track-based detection of the wheel profile of passing railway wheels when the wheels are passing a measuring area by the track.
Wear of flanges of railway wheels is a well-known phenomenon. The wear causes increased operating costs and reduced safety if the presence of the defect is not quickly established so that the carriage in question can be taken out of service and be repaired at a time appropriate to railway operations.
Usually, the presence of correct wheel profile or of wear of the tread or the flange is established by manual examination and inspection of the wheel treads. This is a diffcult examination procedure to control and there are also purely practical difficulties in mechanically measuring and checking the wheel profile.
Today maintenance of the wheels is generally not done on the basis of a conditional supervision but on statistical empiric data, the consequences being that some wheels with defects are not discovered and repaired once the defect occurs, whereas, many faultless wheels are subjected to unnecessary inspection. It is a fact, however, that wear of tread and flange may occur much faster than expected, for example, on account of deficient rail lubrication or following track repair work. It is very important that wheels with a worn tread and/or flange are quickly repaired when the defect occurs since such wheel defects may cause highly increased wear and perhaps destruction of switches etc. and the possibility of derailment by running in curves and switches is greatly increased.
German published specification No. 1,293,810 describes an apparatus for measuring the wheel profile of railway wheels. This apparatus, however, is intended for workshop use and requires dismantling of the wheel pairs which is cumbersome and costly and which is therefore only done in connection with repair and maintenance work. The apparatus cannot be used for measuring a profile on passing carriages since the apparatus requires the wheel pairs to be fixed in the measuring apparatus itself and it can therefore not at all be used for conditional supervision of the wheel profile of passing railway wheels.
U.S. Pat. No. 4,155,526 describes an apparatus for measuring on railway wheels which includes measuring of the flange height when the railway carriages pass a measuring area. The measurement is made by having a number of sensors detect the wheel when the same passes the measuring area and the obtained data are applied for computing the wheel diameter, the tread thickness and the flange height. By this known measuring method there are obtained fairly rough measurements and from these measuring results it is difficult to establish the degree of wear of a wheel since there are only obtained quite few measuring results from the wheel.
It is particularly difficult from the measuring results to say anything about the wheel flange thickness.
It is the object of the invention to provide an apparatus for track-based measuring of the wheel profile, including the flange thickness, of railway wheels of passing carriages whereby there is obtained a precise and accurate detection of the cross-sectional profile of the wheel tread as well as of its flange. The apparatus must therefore be capable of measuring or detecting the geometry precisely and automatically without in any way influencing on railway services.
The above object is achieved by providing an apparatus for track-based detection of a wheel profile of passing railway wheels when the wheels are passing a measuring area by the track, with the apparatus including at least one means for measuring a distance from at least one fixed point by electromagnetic waves to a number of reflection points on the wheel, with the measurement being carried out along at least one baseline. Means are provided for measuring an intermediate position of the passing wheels on the rail in a sidewise or transverse direction during an entire measuring operation over the measuring area, and data processing means, collect, convert, correct and store measured and computed data.
By virtue of the above-noted features of the present invention, a measuring apparatus is provided which has no movable parts since the measuring is carried out along a baseline or a number of baselines which are intersected by the wheel during the passing thereof so that it is simply the wheel itself which forms the movable part and provides detection across an outer profile of the railway wheel. When the baseline or baselines hit the wheel profile in desired places, the distance measurings are carried out and the electronic circuit of the apparatus converts the measuring results into digital values representing the wheel profile applying the measuring of the sideways or transverse position of the wheel as a correction value. Thus, what is obtained is an instantaneous measuring of the wheel profile at the measuring point.
If only one baseline is used, in accordance with further features of the present invention, the apparatus further includes means for measuring the traveling speed or the rate of rotation of the wheel. With such an arrangement, the point to which the distance is measured will move over the wheel profile along a curved path due to the motion of the wheel and the rate of speed of the train or the wheel will therefor have to be used for correcting the measuring results together with information on the direction of the baseline in that the measuring is made when the baseline detects the wheel profile. At the same time any side ways or transverse movement of the wheel must be compensated, and all measuring and correction data must be immediately processed or stored for later processing, with the result being either in the nature of signals corresponding to the wheel profile or signals representing characteristics coefficients stored in the data processor.
In order to enable a measuring operation under optimum conditions and to enable a placement of the measuring apparatus substantially in the track level where it is not affected by protruding parts on the railway carriages, according to further features of the present invention, the baseline is skewed relative to the axle of the wheel of the passing railway wheels.
If the track is yielding, the extent of the deflection depends upon a weight and load of the carriage, and means may be provided for measuring a depression in a vertical direction of the track caused by the weight of the train, whereby it is possible to make precise measurements without the need for supporting the track on the measuring area which is a very difficult and costly task.
By providing a measuring transducer such as, for example, a displacement transducer or like transducer sensitive to motion, a measurement of the distance between the rail base and the frame on which the distance measuring apparatus may be obtained, whereby a deflection in a vertical direction by the passage of the carriage is measured in a simple manner.
In order to enable a comparing of measuring data with the carriage number in such a manner that all data sets are, for example, provided with carriage number and, perhaps, a wheel number, in accordance with the present invention, a wireless carriage identification system may be connected to the data processing means in such a manner that the measuring signals are given a carriage identification signal. A carriage identification signal may be made with a common carriage identification system such as a generally known microwave based system with an antenna placed by the measuring area so that all carriage numbers will have been read when the last carriage leaves the measuring area. The carriage identification system by being connected to the data processor provides data sets with carriage number and, optionally, wheel identification.
The measuring apparatus of the present invention is preferably based upon the use of a laser light and, particularly, post-modulated infra-red laser light, with a receiver means being provided for the reflective laser light from the reflection points and a measuring means for the detection of the reflected laser light. By such an arrangement, it is possible with simple means to focus the light and to obtain a very small and accurate reflection point providing a highly accurate measuring. Such an apparatus may, for example, detect the wheel profile with an accuracy of at least +/-0.1 mm, which is considerably more accurate than necessary.
In order to quickly ascertain whether the wheel profile is within the acceptable tolerances or the wheel requires immediate repair, in accordance with the present invention, further data processing means may be provided for comparing detected wheel profile signals with storage signals corresponding to a correct wheel profile and for comparing characteristic values computed from the detected wheel profile signal with normal values. On the basis of the comparison with the normal values, it is also possible to compute for how long it will be safe to continue using the wheel before instituting any repair work. Furthermore, it is possible to compute how much material will have to be turned off each individual wheel to regain a correct wheel profile.
The measured wheel profiles may be approached by a higher degree polynomial, such as, for example, an eighth degree polynomial by the method of least squares thereby providing suppression of the inevitable noise signals with which the laser light signal is encumbered. It is sufficient to store the computed coefficients which, when the train has passed, are transmitted to the data processor monitoring the wheel maintenance. The wheel profile may be re-stored therein on the basis of the coefficients, and characteristic values such as, for example, flange height, flange width and the maximum deviation between the measured profile and measured reference profile of a perfect wheel may be computed.
In order to enable the apparatus to know precisely when wheels are on the measuring area to be measured and when no train is present in such measuring area, in accordance with further features of the present invention, means are provided for detecting when the train enters the measuring area and detecting when the last carriage leaves such measuring area. The space of time between the trains may be used for transmitting measuring data to a central data base for wheel maintenance and, possibly, for carrying out some additional calculation work if, due to the speed of the train, this cannot be done simultaneously with or immediately after a measuring on the wheel and before the next wheel travels into the measuring area.
The detecting means for detecting when the train enters the measuring area may, for example, be constituted by the measuring apparatus itself, whereby the apparatus is simplified and the ascertainment of whether there is a train in the measuring area or not is performed purely by a program in the apparatus.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings which show, for the purpose of illustration only, several embodiments in accordance with the present invention.